Net Income per Share - Computation of Basic and Diluted Net Income Per Share (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Jan. 24, 2014	Jan. 25, 2013	Jan. 24, 2014	Jan. 25, 2013
Computation Of Earnings Per Share [Line Items]
Net income	$ 192.1	$ 158.1	$ 440.5	$ 331.5
Shares used in basic computation	339.4	359.5	343.7	362.5
Dilutive potential shares related to employee equity award plans	6.8	5.1	7.0	5.1
Dilutive impact of assumed conversion of Convertible Notes	0	0.1	0.7	0.5
Dilutive impact of warrants	0	0	0.3	0
Shares used in diluted computation	346.2	364.7	351.7	368.1
Basic	$ 0.57	$ 0.44	$ 1.28	$ 0.91
Diluted	$ 0.55	$ 0.43	$ 1.25	$ 0.90